Various machines and vehicles, such as tractors, utilize hydraulic systems for transmitting power to implements or tools coupled to the machine or vehicle. For example, back hoes usually use hydraulics to power implements or tools such as jackhammers and augers. The rate at which the implements are moved is typically varied by adjusting the hydraulic flow to the implement. This is typically achieved by adjusting the throttle or RPM up or down to increase or decrease hydraulic flow to the implement.
Many existing older and smaller implements require a relatively low volume flow of hydraulic fluid to operate. To reduce the hydraulic flow to these low flow implements, the vehicle or machine must be throttled down. In some low flow implements, larger machines must be throttled all the way down so as to run at idle. Although throttling the machine or vehicle down accommodates the low flow requirements of such implements, throttling the machine or vehicle down also reduces power. As a result, powering implements that also require large pressures, for example, hammers, result in the engine being killed.
To lower the flow while maintaining throttle or RPM, some systems employ a flow divider or a pressure reducing valve which diverts a large amount of the flow to the sump or tank. Although the use of such diverters enable such systems to reduce the hydraulic flow to the implement while maintaining throttle or RPM, the flow subtracted or diverted to the sump or tank is at high pressure. Because this diversion or flow occurs after exiting major valves, substantial heat is generated resulting in large parasitic losses. Consequently, hydraulic systems which utilize flow diverters to reduce flow to accommodate low flow implements are very inefficient.
As a result, there is a continuing need for a system for supplying hydraulic fluid to an implement that is capable of providing both high flow rates and low flow rates at a given throttle or RPM without heat generation and parasitic losses.
Convention hydraulic systems for supplying hydraulic fluid to implements are controlled by actuating a plurality of different control levers and/or switches. Typically, such systems include a manually operable control for providing bi-directional hydraulic flow to the implement. To free the operator's hands for actuating other controls, conventional systems also include a foot pedal control for providing hydraulic flow to the implement in a single direction. Shifting from manual bi-directional flow control to a single directional flow foot pedal control is typically achieved by shifting the manual control to a neutral position and by further actuating a switch, such as a rocker switch. As a result, shifting between bi-directional flow control and foot pedal flow control requires multiple steps and consume valuable time. Moreover, the multiple manual control levers and/or switches consume valuable control console space and make the design of an ergonomic and user friendly control layout more difficult.
As a result, there is also a continuing need for a system for supplying hydraulic fluid to an implement that provides manual or foot pedal flow control and that preserves console space, is simple and easy to use and manipulate.